Subthreshold and suboptimal desensitization human basophils. I. Kinetics of decay of releasability

The kinetics of desensitization in normal calcium buffer was studied in leukocytes resuspended at a maximum concentration of 50,000 basophils/ml (total available histamine, greater than 5 x 10(-7) M). The time constant of desensitization, k, ranged between 0.01 and 0.02 under subthreshold preincubation conditions (50% inactivation; t 1/2 = 60-120 min). Fractional addition of antigen reduced preincubation histamine release. The degree of IgE bridging required for virtually complete desensitization was complete within the first seconds of incubation of cells with anti-IgE. Hence the slow development of subthreshold and suboptimal desensitization in the presence of calcium must be related to events which occur after IgE cross-linking.